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Stench gas (everything2.com)
241 points by raldi on June 9, 2017 | hide | past | web | favorite | 55 comments

> air allows mines to use a very interesting way to communicate

This is a very important point to remember about subterranean tunnel systems. It is exactly what came to my mind when I watched the Boring Company video about a huge network of 3D tunnels.[1] The tech press, which had probably never even covered a construction project yet alone tunnels, was basically like "what about earthquakes"? But tunnel collapse is not the primary safety issue.

It's fires. Smoke and toxic gases from fires spread very quickly through tunnels.

I am a huge fan of the concept, by the way, but I want to emphasize that most fatalities from traffic tunnels have been from fires (apart from ordinary traffic accidents).[2][3][4][5] And Elon Musk has stated that what makes this vision feasible from a cost perspective is smaller tunnel diameters. Which makes air "communication" all the more accelerated and safety critical. Thus any vision of tunneling without detailing fire safety, evacuation systems and firefighter access is significantly incomplete, as these can add significant cost and fundamentally constrain designs.

[1] https://www.youtube.com/watch?v=u5V_VzRrSBI

[2] https://en.wikipedia.org/wiki/Caldecott_Tunnel_fire

[3] https://en.wikipedia.org/wiki/Gotthard_Road_Tunnel#2001_coll...

[4] https://en.wikipedia.org/wiki/Kaprun_disaster

[5] https://en.wikipedia.org/wiki/Mont_Blanc_Tunnel#1999_fire

> Smoke and toxic gases from fires spread very quickly through tunnels

It's not just the confined-space aspect that causes the fire gases to have such high lethality (although it's certainly extremely significant), it's also the rate of gas production.

Most solids and liquids don't actually burn; they emit flammable gases when exposed to heat, and it's those gases which actually undergo combustion. These gases are created by endothermic processes (pyrolysis and evaporation), and the more heat is available to convert unreactive solid/liquid combustibles into reactive gases, the faster the fire will burn. Therefore, less heat loss (to the outside environment or to non-combustibles) will enable a higher combustion rate and the fire will produce more heat.

Tunnels are quite good at retaining heat, so most of the heat produced by a fire will feed back right into heating combustibles -- enabling devastating heat release rates in the tens to hundreds of megawatts. The heat release rate is roughly proportional to the fire's fuel consumption rate; which will be roughly proportional to the rate of lethal gas (CO/HCN/CO2) production and oxygen depletion.

The radiant heat flux alone can make the fire unapproachable by even appropriately-equipped firefighters -- the massive production of superheated, oxygen depleted, CO/HCN-containing gases can kill -- far beyond the range that the heat flux is deadly.

Great points. An interesting addition is that Musk has also stated that the tunnels would be vacuums (to 5-6 atmospheres) in order to seal against the water table.[1] It's interesting to consider the impacts on fire safety, both in the reduction of risk of spread (a positive) and the difficulties it presents with evacuation from compromised vehicles (a negative).

[1] https://www.ted.com/talks/elon_musk_the_future_we_re_buildin...

Can't watch the video now, but are you saying they are vacuums or pressurized? If they are vacuums, the highest vacuum you can have is -1 atmosphere, I.e. No air.

5-6 atmospheres would be PRESSURIZED, not vacuum.

Also, a vacuum would pull in water from the water table, you'd need pressure to keep it out.

Vacuum would be good for fire prevention, things can't burn if there's no oxygen. Pressure, on the other hand, will greatly amplify fire, if you just pressurize air. If you want to avoid that, you have to pressurize with a neutral gas like nitrogen, which would be expensive if there is any regular amount of gas leakage.

In either case, you'd have to build compartments that were pressure/vacuum proof (think a submarine or spacecraft) -- and in either case, leaving the pressure vessel would pose dire risks to occupants.

I'll try to watch the video when I'm back on WiFi.

From the transcript, this is what the "5 atmospheres" thing meant -- it was about the pressure differential, and that whether the inside is at 1 atm or 0 atm isn't a big deal if the tunnel has to be underground (in which case it already has to stand quite a bit of outside pressure!):

> Exactly. And looking at tunneling technology, it turns out that in order to make a tunnel, you have to — In order to seal against the water table, you've got to typically design a tunnel wall to be good to about five or six atmospheres. So to go to vacuum is only one atmosphere, or near-vacuum. So actually, it sort of turns out that automatically, if you build a tunnel that is good enough to resist the water table, it is automatically capable of holding vacuum.

Thank you for clarifying. I misspoke earlier slightly, but the result is the same: when you build a tunnel strong enough to withstand the water table, it can hold a near vacuum. This helps transport and energy efficiency.. but also presents interesting issues for fire safety.

The minimum pressure of a perfect vacuum is 0 atm, not -1 atm as you say [0].

[0] https://en.m.wikipedia.org/wiki/Vacuum#Measurement

Sure, but it's -1 atm gradient, which is how we commonly measure pressure. I.e., when you fill your car tires to 32 psi, that's 32 psi over atmospheric. When you're talking about pressure, it's the gradient that matters.

It was taught as psia, -g, & -d (or absolute, gauge, and differential) when I was in school, so I read your -1 atm as psid. Your car example would be 32 psi gauge assuming STP, or ~36 psi absolute.

The miners are below the surface and not at 1 atm, so any gauge measures taken there would be psid.

The tunnel becomes something like a stone oven right? I imagine you'd have to let it cool off before trying to approach it.

From the Wikipedia page of the Mont Blanc tunnel fire:

"Some victims escaped to the fire cubicles. The original fire doors on the cubicles were rated to survive for two hours. Some had been upgraded in the 34 years since the tunnel was built to survive for four hours. The fire burned for 53 hours and reached temperatures of 1,000 °C (1,830 °F), mainly because of the margarine load in the trailer, equivalent to a 23,000-litre (5,100 imp gal; 6,100 US gal) oil tanker, which spread to other cargo vehicles nearby that also carried combustible loads."

It was days before the tunnel cooled enough for recovery crews to enter.

With this sort of heat release rate and amount of combustible material, fire doors alone are useless. Even if the fire doors miraculously remain intact and gastight, the walls and doors will eventually conduct enough heat to make the temperature in the fire refuges untenable for human life.

Exactly. The walls act like firebricks.

From the fire perspective, I suppose the positive aspects of musks proposal would be:

Cars are transported on skates, so the engines aren't running during the fire, reducing noxious fumes in the tunnel.

Cars are controlled automatically, reducing the chance of collision.

Since the skates for he cars are controlled automatically, they can be stopped/rerouted much earlier, avoiding bunching cars near the fire.

100 years ago, yesterday, was the worst hard rock mining disaster in the US, in Butte, Montana. They didn't have this way of warning the miners back then and 168 miners died due to a fire in one of the shafts. Most died from asphyxia.

Michael Punke, the author of the Revenant, wrote an excellent non-fiction book about it called "Fire and Brimstone: The North Butte Mining Disaster of 1917".

They remain there until an all-clear is given, which may include a distinct all-clear scent such as wintergreen.

If you search for "stench gas" you will find some... interesting photos of the control panel for these systems:


(Something about buttons marked "release stench gas" and "release anti-stench gas" seem amusing in a rather comical fashion.)

Something OCD in me is rather disturbed by the "release stench gas" being located to the right of the "anti-stench gas".

It should clearly (or likely) be the other way around, at least in any country with a left-to-right reading order, OCD or not :)

We scan information faster in the preferred reading direction, and flipping the warning​ gas on half a second earlier will likely, sooner or later save somebody from harm. Not that there aren't other ways to improve safety in mines, but each small part counts, I guess?

Not pictured, but right next to this machine is the "garry gum" and "anti-garry gum" dispenser.

Just reading about that article triggered an olfactory memory of the related compound 2-mercaptoethanol (or beta-mercaptoethanol as it was labeled in the lab). Used to reduce disulfide links in proteins (edit: see more correct response below) so that they would unravel a bit and separate by size more as they travel through the western blot matrix.

Unlike carbon monoxide this compound had a very "this will kill you" smell to it.


2ME is the "gas leak" additive that gets put into gasoline.

It smells like sulfur + burnt rice crackers to me... It's actually not that dangerous of a compound - I've spilled it on myself gloveless and it's not a big deal.

Also a bit of a possibly overpedantic note - you can run gels without reducing the disulfide bonds, but typically those proteins will run through the gel faster, not slower because of a more compact form. Because not all proteins have disulfides, if you reduce them first, it creates a predictable relationship between the protein size and the migration velocity, which is the desirable property, not speed.

Are you thinking of Ethanethiol / ethyl mercaptan? I can't find reference to 2-Mercaptoethanol being used as an odorant. https://en.m.wikipedia.org/wiki/Ethanethiol

Thanks for the additional note, I haven't done lab work in many years and that is more correct.

Context matters - I worked in a surface science lab, so lots of gold monolayers being made with sulfur compounds. While I wouldn't say they're remotely pleasant, I'm so used to them that it's more like a gradient where you're like "this could be worse". Pure chemicals are well...pure. It's when it smells like uncontrolled biology that I get uncomfortable.

is that the nasty sour smelling chemical? sort of like sulfur, vinegar, burnt gunpowder, and vodka, mixed together? i used to get a whiff of it at my dad's bench at his workplace.

Acetic acid and Butyric acid. Used for those clear tool handles. [1][2] It gets nastier once you realize you are smelling the odor of vomit with hints of vinegar.

[1] https://en.wikipedia.org/wiki/Butyric_acid

[2] https://en.wikipedia.org/wiki/Cellulose_acetate

Thanks so much for that! I've been wondering for years what that unique smell (from various clear-handled Newtonian tools) was.

I guess it's used where clear or somewhat- clear plastic is used. But does BPA have the same smell over time?

No worse then a Hershey's chocolate bar...

For anyone unfamiliar with the connection, Hershey's milk chocolate is made with a process that produces butyric acid:


it isn't that. my dad worked in biochemistry and that's what i'm talking about.

my shitty screwdrivers have the smell you're talking about.

My mistake -- I was thinking of a Newtonian work bench. :-)

Maybe. To me it had a very "industrial-fish" smell is the best way I can put it. Not fishy like Thai fish oil, but maybe like an ocean oil spill site puréed, baked in the sun and concentrated? I remember it provoked a visceral reaction to not smell it more.

that sounds like thiolacetic acid, or posibly triflic acid (trifluoromethanesulfonic acid).

Everything2 is still around?!?! Awesome.

Yeah, Jay Bonci is still running the damn thing. And people still log in. And nobody seems to have any plans to shut it down.

Dude even still writes root logs:



Whenever a big event happens, like some big e2 celebrity dies, there's a surge of people logging into the site to pay their respects. Weddings and funerals, they say, but for e2 it seems to be only funerals.

It fills my heart with glee when I see sites o' yesteryear still around. Love Everything2. Glad perlmonks isn't the only site still running that code.

I know right? Sites like these used to be linked so often. Now that this is no longer the case, I've easily forgotten about these old sites.

If our noses were "sharper", i.e., able to distinguish on a deeper more meaningful level like a dog, could we transmit complex information with olfactory encoding?

Right now the smells are simple signals; I'm curious if a scent could be engineered to contain a language. Like paper and writing.

I'm asking for my story, in which sapient rats struggle against two-legged monsters with opposable thumbs.

I've wondered if one could build a device that outputs different combinations of distinct scents for training dogs. Like condition the dog to understand "sit" = "bacon smell" and "shake" = "cat". My theory was that dogs have more cognitive resources dedicated to processing olfactory information and so they could also be trained to understand and perform more complex tasks. Like, "bacon + cat + shoe smell" = "bark while running left"

For those still curious, I found something of answer here:


I wonder if we could tie this to Jenkins for when a build breaks. Would make for a nicer alternative than sirens and flashing lights, although I suspect people would tend to clear the office...

It smells absolutely wretched, and is totally unmistakable.

Had it go off on a couple sites I've been on, and it's remarkable how it reaches every corner of the mine.

Would love to hear more. What prompted it, and how did everyone respond? Was the wintergreen "all clear" signal used after the problem was resolved?

I instinctively hovered my mouse over the link to wintergreen, my brain fully expecting to click and experience the smell - as I would with any image, video, or sound. Took me a few seconds to manage expectations!

"Employees of the Union Oil Company of California reported first in 1938 that turkey vultures would gather at the site of any gas leak. After finding that this was caused by traces of ethanethiol in the gas it was decided to boost the amount of ethanethiol in the gas, to make detections of leaks easier"

Aw, I thought that story was going to end with them breeding vast flocks of turkey vultures to patrol the pipes.

And then stocking the area with extra carrion to sustain all the new vultures? Hmmmm what could go wrong...

Same principle in fire alarm for the deaf:


They use wasabi.

I remember seeing this for sale on BOC's website when looking for CO2 a while back (https://www.boc.co.nz/shop/en/nz/stench-gas). I briefly considered buying some for nefarious purposes, but I think I figured that they probably wouldn't just sell it to any random person.

Reminds me of the Friends' episode where Ross goes on and on with the (bored and weirded out) pizza delivery girl about the smelly chemical added to natural gas in order to make it olfactible & safer to use.

Found it... https://youtu.be/kH5JhYsfNMA?t=1m10s

And if you've ever wondered whose blood those regulations arose from, it's the 300 souls lost in the New London School Explosion:


Yeah, we lose the collective memory of the "why" behind many of our regulations. Thanks for telling me about this. I certainly did not know!

Same compound that is added to propane

I think my family went to that exhibit while I was pre adolescent. I got scared so only my mother & sister went, while I stayed topside with my father. We window shopped the souvenir shop

Nowadays my sister suffers claustrophobia & I feel most comfortable shoved into small crooks. But I think I was mostly offset by anxiety related to ventilation

Visited Timmins this May, another northern Ontario city. It was snowing

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